1. Field of the Invention
The present invention relates to image stabilization of image capturing data.
2. Description of the Related Art
A digital image easily allows an enlarged-scale display over 100% using a personal computer. In an enlarged image, an image blur due to even a slight camera shake stands out. For this reason, as an image capturing device of a digital camera gains higher resolutions, a process for correcting for camera shake at the time of imaging has received a lot of attention.
An image-stabilization method includes those implemented by hardware and software. In a method implemented by hardware, a gyro sensor is mounted on a camera, and the influence of camera shake is eliminated by driving a lens and image capturing device to cancel vibrations of the camera during exposure based on an output signal from the gyro sensor. An image-stabilization method by means of a lens optical system is described in, for example, Japanese Patent Laid-Open No. 2002-214657.
The hardware image-stabilization method poses problems related to an increase in number of components and manufacturing cost. When a similar function is to be implemented in an inexpensive digital camera, a software image-stabilization method is required.
As the software image-stabilization method, a method for synthesizing an image obtained by short exposure (to be referred to as a short exposure image hereinafter) and that obtained by long exposure (to be referred to as a long exposure image hereinafter) has been proposed (for example, Japanese Patent Laid-Open No. 2002-258351). Also, a method of acquiring a plurality of short exposure images, and synthesizing these images has been proposed (for example, Japanese Patent Laid-Open Nos. 2006-074693 and 2006-086762).
The method of Japanese Patent Laid-Open No. 2002-258351 corrects high-frequency components of the long exposure image using the short exposure image to recover an image blur. The method of Japanese Patent Laid-Open No. 2006-074693 aligns a plurality of short exposure images obtained by exposure that time-divisionally controls opening and closing timings of a shutter (to be referred to as time-division exposure), so as to reduce their difference, and synthesizes these images, thereby recovering from an image blur. Likewise, the method of Japanese Patent Laid-Open No. 2006-086762 synthesizes a plurality of images after blur correction while aligning their positions, thereby recovering an image blur.
However, the methods of Japanese Patent Laid-Open Nos. 2006-074693 and 2006-086762 suffer the following problems. In order to appropriately recover an image blur, a plurality of short exposure images are appropriately synthesized according to their displacement amounts. In other words, the appropriate image blur recovery process requires to accurately acquire displacement amounts. Therefore, a displacement amount between a given short exposure image and that captured immediately before or after that image has to be calculated. However, a process for accurately calculating a displacement amount and that for deforming and synthesizing images in correspondence with the displacement amount require very high calculation cost, resulting in a continuous shooting speed drop and a decrease in number of image capturing data that can be buffered.